TY - JOUR
T1 - Large-scale patterns of diversification in the widespread legume genus senna and the evolutionary role of extrafloral nectaries
AU - Marazzi, Brigitte
AU - Sanderson, Michael J.
N1 - Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2010/12
Y1 - 2010/12
N2 - Unraveling the diversification history of old, species-rich and widespread clades is difficult because of extinction, undersampling, and taxonomic uncertainty. In the context of these challenges, we investigated the timing and mode of lineage diversification in Senna (Leguminosae) to gain insights into the evolutionary role of extrafloral nectaries (EFNs). EFNs secrete nectar, attracting ants and forming ecologically important ant-plant mutualisms. In Senna, EFNs characterize one large clade (EFN clade), including 80% of its 350 species. Taxonomic accounts make Senna the largest caesalpinioid genus, but quantitative comparisons to other taxa require inferences about rates. Molecular dating analyses suggest that Senna originated in the early Eocene, and its major lineages appeared during early/mid Eocene to early Oligocene. EFNs evolved in the late Eocene, after the main radiation of ants. The EFN clade diversified faster, becoming significantly more species-rich than non-EFN clades. The shift in diversification rates associated with EFN evolution supports the hypothesis that EFNs represent a (relatively old) key innovation in Senna. EFNs may have promoted the colonization of new habitats appearing with the early uplift of the Andes. This would explain the distinctive geographic concentration of the EFN clade in South America.
AB - Unraveling the diversification history of old, species-rich and widespread clades is difficult because of extinction, undersampling, and taxonomic uncertainty. In the context of these challenges, we investigated the timing and mode of lineage diversification in Senna (Leguminosae) to gain insights into the evolutionary role of extrafloral nectaries (EFNs). EFNs secrete nectar, attracting ants and forming ecologically important ant-plant mutualisms. In Senna, EFNs characterize one large clade (EFN clade), including 80% of its 350 species. Taxonomic accounts make Senna the largest caesalpinioid genus, but quantitative comparisons to other taxa require inferences about rates. Molecular dating analyses suggest that Senna originated in the early Eocene, and its major lineages appeared during early/mid Eocene to early Oligocene. EFNs evolved in the late Eocene, after the main radiation of ants. The EFN clade diversified faster, becoming significantly more species-rich than non-EFN clades. The shift in diversification rates associated with EFN evolution supports the hypothesis that EFNs represent a (relatively old) key innovation in Senna. EFNs may have promoted the colonization of new habitats appearing with the early uplift of the Andes. This would explain the distinctive geographic concentration of the EFN clade in South America.
KW - Andes
KW - Ant-plant mutualism
KW - Diversification rates
KW - Key innovation
KW - Leguminosae
KW - Radiation
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U2 - 10.1111/j.1558-5646.2010.01086.x
DO - 10.1111/j.1558-5646.2010.01086.x
M3 - Article
C2 - 21133898
AN - SCOPUS:78650028282
VL - 64
SP - 3570
EP - 3592
JO - Evolution; international journal of organic evolution
JF - Evolution; international journal of organic evolution
SN - 0014-3820
IS - 12
ER -